arch_topology: Convert switch block to if block

We only need to take care of one case here (CPUFREQ_NOTIFY) and there is
no need to add an extra level of indentation to the case specific code
by using a switch block. Use an if block instead.

Also add some blank lines to make the code look better.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Juri Lelli <juri.lelli@arm.com>
Tested-by: Juri Lelli <juri.lelli@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>